a.c~

用AVR的模拟SPI总线读取

//头文件
#include <mega64.h>   
//  
//IO方向
#define cprotb 0b1111110
#define cprotc 0b0011111
#define cportd 0x0	
//清0和置1
#define set_0 0b00000001 
#define set_1 0b00000010
#define set_2 0b00000100 
#define set_3 0b00001000 
#define set_4 0b00010000 
#define set_5 0b00100000
#define set_6 0b01000000 
#define set_7 0b10000000 
#define clr_0 0b11111110 
#define clr_1 0b11111101 
#define clr_2 0b11111011 
#define clr_3 0b11110111
#define clr_4 0b11101111 
#define clr_5 0b11011111 
#define clr_6 0b10111111 
#define clr_7 0b01111111  
#define qs_so (PINA&set_0) 
#define clr_cs PORTA &= clr_1 
#define set_cs PORTA |= set_1 
#define clr_sck PORTA &= clr_2 
#define set_sck PORTA |= set_2
unsigned int hsq6675();
void main()
{   
    unsigned int jiwd;
    PORTA = 0B011;
    DDRA = 0B110;
    while(1)
    jiwd = hsq6675();
}                    
unsigned int hsq6675()
{ 
    unsigned int jiwd; 
    unsigned char jzsj;
    float jfwd;
    jzsj = 16;
    jiwd = 0;
    clr_sck;
    clr_cs;
    while(jzsj != 0)
    {
        set_sck;
        jiwd = jiwd<<1;
        if(qs_so == 0)
        {
            jiwd &= 0xfffe;
        }
        else
        { 
            jiwd |= 1;
        }
        clr_sck;  
        --jzsj;
    }   
    set_cs; 
    clr_sck;
    if(jiwd&0x4 == 0)
    { 
        jiwd = 0xffff;
    }
    else
    { 
        jiwd = jiwd>>3;
    } 
    jfwd = (float)(jiwd)*0.25;
    return(jiwd);
}